Figure 4.

Monoallelic centromeric recruitment of the Igh locus during B cell development. (a) Centromeric location of one Igh allele in bone marrow pre–B cells. Large and small pre–B cells and activated splenic B cells were analyzed by three-color three-dimensional DNA FISH with V_HJ558 (red), C_γ1 (green) and γ-satellite (γ-sat; blue) probes. The relative positions of the three signals are shown in confocal sections through the nuclei of these cells. (b) Association of the distal V_HJ558 gene domain with centromeric clusters. Enlargements show the orientation and decontraction of the Igh locus at γ-satellite clusters. Below images, distance between the V_HJ558 and C_γ1 probe signals. (c) Monoallelic recruitment of the Igh locus to centromeres. Data represent the percentage of cells showing association of one Igh allele with centromeric heterochromatin in various B cell developmental stages, sorted as indicated in Supplementary Fig. 1 online. Actual numbers and sample sizes are in Supplementary Table 2 online. (d) Preferential location of widely separated Igh alleles at the centromeres. The cells showing monoallelic centromeric recruitment were subdivided into a population of cells containing an Igh allele with wide separation (1–1.5 μm) of the V_HJ558 and C_γ1 genes. Data represent the percentage of centromeric recruitment of the widely separated Igh allele in this cell population for large and small pre–B cells and activated (Act.) splenic B cells.